For a number of years diisopropoxy titanium (IV)-bisacetylacetonate, titanium-acetylacetonate for short, has been successfully used for this purpose. The disadvantage of titanium acetylacetonate resides in its own dark red color and in the discoloration of materials to which it was added, which is particularly noticeable with printing inks, especially, with white printing inks.
In the search for titanium-based, non-discoloring, adhesion promoting additives the following criteria should be met:
(a) Compatibility with printing ink binders. Upon addition of the additives no gel formation of the printing ink must occur. Increase in viscosity due to cross-linking should not occur; PA1 (b) The additive should have as little color of its own as possible; PA1 (c) Sufficient adhesion promoting effect.
The titanium chelate of 2-ethyl-hexanediol-1,3 (also referred to as octylene glycol) with a molar ratio of 4:1, OGT-HV for short, meets requirements (a) and (b), but is not sufficiently effective as an adhesion promoter in a nitrocellulose printing ink on polypropylene foil. The standard set by titanium acetylacetonate was not achieved.